Video signal processing systems may include the capability to receive and process various types of signals. For example, certain television signal processing apparatus (which may be a device including a display device, e.g., a television set, or may not include a display device, e.g., a set-top box) may provide for receiving and processing both an enhanced definition television signal, such as a high-definition television (HDTV) signal or progressive-scan type of signal (collectively, “enhanced performance television signal”), and may also provide for processing composite video or other standard definition (480-lines, interlaced) television (SDTV) signals. Usually, the user of a video system capable of processing HD/progressive-scan television signals would prefer to view a television program via an HD signal so as to enjoy the improved picture quality possible with HDTV signal processing.
However, use of an enhanced-performance video signal, such as HDTV or progressive scan signals, may make certain features common to standard definition televisions difficult or impossible to use. For example, many televisions include the capability to receive and decode auxiliary information that may be included in a television signal. Specific examples of such auxiliary information include teletext data, closed caption data, program guide data, and the like. Most analog television signals include such auxiliary information in a portion of the signal that does not usually carry programming information, e.g., the vertical blanking interval (VBI) of an NTSC signal. Auxiliary information may also be included in digital television signals by, for example, dedicating a particular stream of digital data packets to the auxiliary information data.
However, not all enhanced performance or HDTV signals include auxiliary information and, therefore, a user may be unable to use a feature such as closed captioning when viewing an HDTV program in the same way that he could for a NTSC program. That is, some of the new video signal interfaces, e.g., progressive scan and high definition video, do not have embedded auxiliary information such as closed caption data. So, the user who wants the improved video performance offered by the new video signal interfaces cannot have both the improved video performance and auxiliary information.